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1 // Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file | 1 // Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file |
2 // for details. All rights reserved. Use of this source code is governed by a | 2 // for details. All rights reserved. Use of this source code is governed by a |
3 // BSD-style license that can be found in the LICENSE file. | 3 // BSD-style license that can be found in the LICENSE file. |
4 | 4 |
5 library dart.pkg.collection.canonicalized_map; | |
6 | |
7 import 'dart:collection'; | 5 import 'dart:collection'; |
8 | 6 |
9 import 'utils.dart'; | 7 import 'utils.dart'; |
10 | 8 |
11 /** | 9 /// A map whose keys are converted to canonical values of type `C`. |
12 * A map whose keys are converted to canonical values of type `C`. | 10 /// |
13 * | 11 /// This is useful for using case-insensitive String keys, for example. It's |
14 * This is useful for using case-insensitive String keys, for example. It's more | 12 /// more efficient than a [LinkedHashMap] with a custom equality operator |
15 * efficient than a [LinkedHashMap] with a custom equality operator because it | 13 /// because it only canonicalizes each key once, rather than doing so for each |
16 * only canonicalizes each key once, rather than doing so for each comparison. | 14 /// comparison. |
17 * | 15 /// |
18 * By default, `null` is allowed as a key. It can be forbidden via the | 16 /// By default, `null` is allowed as a key. It can be forbidden via the |
19 * `isValidKey` parameter. | 17 /// `isValidKey` parameter. |
20 */ | |
21 class CanonicalizedMap<C, K, V> implements Map<K, V> { | 18 class CanonicalizedMap<C, K, V> implements Map<K, V> { |
22 final Function _canonicalize; | 19 final Function _canonicalize; |
23 | 20 |
24 final Function _isValidKeyFn; | 21 final Function _isValidKeyFn; |
25 | 22 |
26 final _base = new Map<C, Pair<K, V>>(); | 23 final _base = new Map<C, Pair<K, V>>(); |
27 | 24 |
28 /** | 25 /// Creates an empty canonicalized map. |
29 * Creates an empty canonicalized map. | 26 /// |
30 * | 27 /// The [canonicalize] function should return the canonical value for the |
31 * The [canonicalize] function should return the canonical value for the given | 28 /// given key. Keys with the same canonical value are considered equivalent. |
32 * key. Keys with the same canonical value are considered equivalent. | 29 /// |
33 * | 30 /// The [isValidKey] function is called before calling [canonicalize] for |
34 * The [isValidKey] function is called before calling [canonicalize] for | 31 /// methods that take arbitrary objects. It can be used to filter out keys |
35 * methods that take arbitrary objects. It can be used to filter out keys that | 32 /// that can't be canonicalized. |
36 * can't be canonicalized. | |
37 */ | |
38 CanonicalizedMap(C canonicalize(K key), {bool isValidKey(Object key)}) | 33 CanonicalizedMap(C canonicalize(K key), {bool isValidKey(Object key)}) |
39 : _canonicalize = canonicalize, | 34 : _canonicalize = canonicalize, |
40 _isValidKeyFn = isValidKey; | 35 _isValidKeyFn = isValidKey; |
41 | 36 |
42 /** | 37 /// Creates a canonicalized map that is initialized with the key/value pairs |
43 * Creates a canonicalized map that is initialized with the key/value pairs of | 38 /// of [other]. |
44 * [other]. | 39 /// |
45 * | 40 /// The [canonicalize] function should return the canonical value for the |
46 * The [canonicalize] function should return the canonical value for the given | 41 /// given key. Keys with the same canonical value are considered equivalent. |
47 * key. Keys with the same canonical value are considered equivalent. | 42 /// |
48 * | 43 /// The [isValidKey] function is called before calling [canonicalize] for |
49 * The [isValidKey] function is called before calling [canonicalize] for | 44 /// methods that take arbitrary objects. It can be used to filter out keys |
50 * methods that take arbitrary objects. It can be used to filter out keys that | 45 /// that can't be canonicalized. |
51 * can't be canonicalized. | |
52 */ | |
53 CanonicalizedMap.from(Map<K, V> other, C canonicalize(K key), | 46 CanonicalizedMap.from(Map<K, V> other, C canonicalize(K key), |
54 {bool isValidKey(Object key)}) | 47 {bool isValidKey(Object key)}) |
55 : _canonicalize = canonicalize, | 48 : _canonicalize = canonicalize, |
56 _isValidKeyFn = isValidKey { | 49 _isValidKeyFn = isValidKey { |
57 addAll(other); | 50 addAll(other); |
58 } | 51 } |
59 | 52 |
60 V operator [](Object key) { | 53 V operator [](Object key) { |
61 if (!_isValidKey(key)) return null; | 54 if (!_isValidKey(key)) return null; |
62 var pair = _base[_canonicalize(key)]; | 55 var pair = _base[_canonicalize(key)]; |
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107 return pair == null ? null : pair.last; | 100 return pair == null ? null : pair.last; |
108 } | 101 } |
109 | 102 |
110 Iterable<V> get values => _base.values.map((pair) => pair.last); | 103 Iterable<V> get values => _base.values.map((pair) => pair.last); |
111 | 104 |
112 String toString() => Maps.mapToString(this); | 105 String toString() => Maps.mapToString(this); |
113 | 106 |
114 bool _isValidKey(Object key) => (key == null || key is K) && | 107 bool _isValidKey(Object key) => (key == null || key is K) && |
115 (_isValidKeyFn == null || _isValidKeyFn(key)); | 108 (_isValidKeyFn == null || _isValidKeyFn(key)); |
116 } | 109 } |
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